In many cases, the production of natural gas is complicated by the presence of certain heavy hydrocarbons in the subterranean formation in which the gas is found. Under conditions prevailing in the subterranean reservoirs, the heavy hydrocarbons may be partially dissolved in the compressed gas or finely divided in a liquid phase. The decrease in temperature and pressure attendant to the upward flow of gas as it is produced to the surface result in the separation of solid hydrocarbonaceous material from the gas. Such solid hydrocarbons may form in certain critical places such as on the interior wall of the production string, thus restricting or actually plugging the flow passageway.
Various processes have been developed to prevent the formation of such precipitates or to remove them once they have formed. These include mechanical removal of the deposits and the batchwise or continuous injection of a suitable solvent. Recovery of one such class of heavy hydrocarbons, i.e. diamondoid materials, from natural gas is detailed in commonly assigned co-pending U.S. patent application Ser. No. 405,119, filed Sept. 7, 1989, now U.S. Pat. No. 4,952,748 which is a continuation of U.S. Pat. No. 358,758, filed May 26, 1989, now abandoned, as well as U.S. patent applications Ser. No. 358,759, now U.S. Pat. Nos. 4,952,747, 358,760, now U.S. Pat. Nos. 4,952,749, and 358,761, all filed May 26, 1989. The text of these U.S. Patent Applications is incorporated herein by reference.
Certain hydrocarbonaceous streams, for example certain natural gas streams, contain a small proportion of diamondoid compounds. These high boiling, saturated, three-dimensional polycyclic organics are illustrated by adamantane, diamantane, triamantane and various side chain substituted homologues, particularly the methyl derivatives. These compounds have high melting points and high vapor pressures for their molecular weights and have recently been found to cause problems during production and refining of hydrocarbonaceous minerals, particularly natural gas, by condensing out and solidifying, thereby clogging pipes and other pieces of equipment. For a survey of the chemistry of diamondoid compounds, see Fort, Jr., Raymond C., The Chemistry of Diamond Molecules, Marcel Dekker, 1976.
In recent times, new sources of hydrocarbons have been brought into production which, for some unknown reason, have substantially larger concentrations of diamondoid compounds. Whereas in the past, the amount of diamondoid compounds has been too small to cause operational problems such as production cooler plugging, now these compounds represent both a larger problem and a larger opportunity. The presence of diamondoid compounds in natural gas has been found to cause plugging in the process equipment requiring costly maintenance downtime to remove. On the other hand, these very compounds which can deleteriously affect the profitability of natural gas production are themselves valuable products.